The present application claims priority under 35 U.S.C xc2xa7119 based upon Swiss Patent Application 2001 1194/01 No. filed Jun. 28, 2001.
The invention concerns a device for the metered delivery of a viscous liquid.
A device for the metered delivery of a viscous liquid is known from the Singapore patent application SG 0074739. This device comprises a pump body with a drill hole which connects an intake chamber and a discharge chamber. In this drill hole, two pistons are moved back and forth between the intake chamber and the discharge chamber. A slot of variable width is formed between the faces of the two pistons so that the liquid in the intake chamber fills the slot and is pressed out of the slot into the discharge chamber. To guide the pistons, guide rails are present which are guided in further, parallel running drill holes.
This device has two disadvantages. When used for applying adhesive, it can happen that flakes of silver contained in the adhesive make their way to the outside of the pump body and from there into the drill holes which accommodate the guide rails which leads to the guide rails sticking. Furthermore, the friction of the guide rails in the drill holes is too great.
The object of the invention is to rectify the above mentioned shortcomings.
The invention shows on the one hand an improved drive mechanism as well as certain constructive measures which prevent the drive mechanism from sticking and, on the other hand, a pump body which is particularly suitable for the metered delivery of adhesives which contain flakes of silver. This pump body distinguishes itself in that the drill hole which connects the intake chamber with the discharge chamber is extended whereby the two pistons which are moved back and forth in the drill hole form a slot seal at the ends of the drill hole. In order that the slot seal is sufficiently tight, the piston and the pump body or a sleeve incorporated into the pump body which contains the drill hole are, on the one hand, paired with suitable materials and, on the other hand, are manufactured with the highest precision.
In the following, an embodiment of the invention is explained in more detail based on the drawing.